The present invention relates to tissue stimulation systems and more particularly to display interfaces having graphical depictions used during a stimulation session. One example of a stimulation system is a spinal cord stimulation system (“SCS”). Spinal cord stimulation is a well accepted clinical method for reducing pain in certain populations of patients. An SCS system typically includes an Implantable Pulse Generator (IPG) or a radio-frequency (RF) transmitter and receiver, electrodes, electrode leads, and when necessary, lead extensions. The electrodes are implanted along the dura of the spinal cord, and the IPG or RF transmitter generates electrical pulses that are delivered, through the electrodes, to the dorsal column and dorsal root fibers within the spinal cord. Individual electrode contacts (the “electrodes”) are arranged in a desired pattern and spacing in order to create an electrode array. Individual wires within one or more electrode leads connect with each electrode in the array. The electrode leads exit the spinal column and attach to one or more electrode lead extensions, when necessary. The electrode leads or extensions are typically tunneled around the torso of the patient to a subcutaneous pocket where the IPG or RF-receiver is implanted.
Spinal cord stimulators and other stimulation systems are known in the art. For example, an implantable electronic stimulator is disclosed in U.S. Pat. No. 3,646,940 issued Mar. 7, 1972 for “Implantable Electronic Stimulator Electrode and Method” that provides timed sequenced electrical impulses to a plurality of electrodes. As another example, U.S. Pat. No. 3,724,467 issued Apr. 3, 1973 for “Electrode Implant For The Neuro-Stimulation of the Spinal Cord,” teaches an electrode implant for the neuro-stimulation of the spinal cord. A relatively thin and flexible strip of physiologically inert plastic is provided as a carrier on which a plurality of electrodes are formed. The electrodes are connected by leads to an RF receiver, which is also implanted.
In U.S. Pat. No. 3,822,708, issued Jul. 9, 1974 for “Electrical Spinal Cord Stimulating Device and Method for Management of Pain,” another type of electrical spinal cord stimulation device is taught. The device disclosed in the '708 patent has five aligned electrodes, which are positioned longitudinally on the spinal cord. Electrical pulses applied to the electrodes block perceived intractable pain, while allowing passage of other sensations. A patient operated switch allows the patient to adjust the stimulation parameters.
An SCS system treats chronic pain by providing electrical stimulation pulses through the electrodes of an electrode array located at the distal end of a lead placed epidurally next to a patient's spinal cord. The combination of electrodes used to deliver stimulation pulses to the targeted tissue constitutes an electrode configuration. In other words, an electrode configuration represents the polarity, being positive, negative, or zero and relative percentage of the current or voltage provided through each of the electrodes.
Electrode arrays used with known SCS systems may employ between 1 and 16 electrodes on a lead. Electrodes are selectively programmed to act as anodes, cathodes, or left off, creating an electrode configuration. The number of electrodes available, combined with the ability to generate a variety of complex stimulation pulses, presents a huge selection of electrode configurations and stimulation parameter sets to the clinician. When an SCS system is implanted, a procedure is performed to select one or more effective electrode configurations and stimulation parameter sets for a particular patient. Such a session of applying various stimulation parameters and electrode configurations may be referred to as a “fitting” or “programming” session. Additionally, a series of electrode configurations to be applied to a patient may be organized in a steering table or in another suitable manner.
Other parameters that may be controlled or varied in SCS are the frequency of pulses provided through the electrode array, pulse width, and the strength (amplitude) of pulses delivered. Amplitude may be measured in milliamps, volts, etc., as appropriate, depending on whether the system provides stimulation from current sources or voltage sources. With some SCS systems, the distribution of the current/voltage across the electrodes (including the case of the pulse generator or receiver, which may act as an electrode) may be varied such that the current is supplied via numerous different electrode configurations. In different configurations, different combinations of electrodes may provide current (or voltage) in different relative percentages of positive and negative current (or voltage). Moreover, there may be some electrodes that remain inactive for certain electrode configurations, meaning that no current is applied through the inactive electrode.
Previous SCS technology identified these parameters and effectuated stimulation through an electrode array using specific electrode configurations. These parameters, including distribution (if available), configuration, strength, pulse width, etc., are programmed after implantation in a “fitting” procedure. During the fitting, an extremely large number of possible combinations of stimulation parameters may be tested.
In order to test the effectiveness on a particular patient of various stimulation parameters and electrode configurations, it is necessary to provide a series of stimulation parameters in a systematic method. Several such systems exist including the systems disclosed in U.S. Pat. No. 6,393,325, herein incorporated by reference in its entirety, wherein a patient may direct the movement of the stimulus current through a suitable interface.
During a programming session, a clinician and a patient may use a display screen, such as the one described in U.S. Pat. No. 6,622,048, herein incorporated by reference in its entirety. Such a display screen may include a depiction of the human figure divided into body regions.
Other display graphics may be developed to make the programming efficient, easy, and accurate and to readily convey the values of stimulation parameters to a clinician and patient. There is a need to display the different electrodes of the array and to depict the electrodes as an anode or a cathode and to depict any current distribution among the implanted electrodes. Displays also should graphically convey the applied relative values of amplitude, pulse width and pulse rate. Such display graphics are described herein, such as icons for electrode configurations and pulse parameters. These graphics convey information regarding the values of the stimulation parameters and electrode configurations in an easily understood graphical format.